Terminal apparatus and control channel detecting method

ABSTRACT

A radio communication base station device which can reduce the number of judgment times for a control signal in a mobile station, thereby suppressing power consumption by the mobile station. The radio communication base station device ( 100 ) includes: a mapping setting unit ( 122 ) which sets a mapping method in a mapping unit ( 102 ); the mapping unit ( 102 ) which maps a control signal to respective mobile stations to any of subcarriers constituting the OFDM symbol according to the mapping method set by the mapping setting unit ( 122 ); an MCS setting unit ( 121 ) which references a mapping table in which correlation between a plurality of MCS having different MCS levels and mapping methods is set according to the judgment result of the mapping setting unit ( 122 ) and sets MCS in encoding/modulation units ( 101 - 1  to  101 - n ).

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of application Ser. No. 12/522,368filed Jul. 7, 2009, which is a national stage of PCT/JP2008/050137 filedSep. 1, 2008, which is based on Japanese Application No. 2007-001726filed Jan. 9, 2007, the entire contents of each of which areincorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a radio communication base stationapparatus and a control signal mapping method.

BACKGROUND ART

In recent years, in the field of radio communication, especially inmobile communication, a variety of information such as images and datain addition to speech is transmitted. The demand for higher speedtransmission is expected to further increase in the future, and, toperform high-speed transmission, a radio transmission scheme thatutilizes limited frequency resources more effectively and achieves hightransmission efficiency is in demand.

OFDM (Orthogonal Frequency Division Multiplexing) is one of radiotransmission techniques, to meet these demands. OFDM is one ofmulticarrier communication techniques, whereby data is transmitted inparallel using a large number of subcarriers, and it is known that OFDMhas features of providing high frequency efficiency and reducinginter-symbol interference in a multipath environment and is effective toimprove transmission efficiency.

Studies are being conducted to perform frequency scheduling transmissionand frequency diversity transmission using this OFDM on the downlink,when a radio communication base station apparatus (hereinafter simply“base station”) frequency-domain-multiplexes on a plurality ofsubcarriers data for a plurality of radio communication mobile stationapparatuses (hereinafter simply “mobile stations”).

In frequency scheduling transmission, the base station adaptivelyallocates subcarriers for mobile stations, based on the received qualityof each frequency band in each mobile station, so that it is possible toobtain a maximum multi-user diversity effect. This frequency schedulingtransmission is mainly suitable for mobile stations moving at low speed.Meanwhile, to perform frequency scheduling transmission, feedback ofreceived quality information from the mobile stations to the basestation is necessary, and therefore, frequency scheduling transmissionis not suitable for the mobile station moving at high speed. Further,frequency scheduling transmission is usually performed on every resourceblock grouping a plurality of neighboring subcarriers. That is, infrequency scheduling transmission, data for mobile stations is mapped tosubcarriers collectively per resource block, that is, localized mappingis performed, and therefore, not much high frequency diversity effect isobtained.

By contrast with this, in frequency diversity transmission, data formobile stations is mapped to subcarriers in a distributed manner overthe entire band, that is, distributed mapping is performed, so that ahigh frequency diversity effect can be obtained. Further, frequencydiversity transmission does not require received quality informationfrom the mobile stations, and therefore, frequency diversitytransmission is a useful scheme where frequency scheduling transmissionis difficult to apply. On the other hand, frequency diversitytransmission is performed regardless of received quality in the mobilestations, and therefore it is not possible to obtain multi-userdiversity effect such as in frequency scheduling transmission.

Further, to perform frequency scheduling transmission, the base stationtransmits, to the mobile stations of data transmission destinations persubframe, control signals formed with mobile station IDs (i.e. userIDs), resource block numbers, modulation and coding schemes (MCSs) fordata channels, types of control information and so on, at the beginningof each subframe, prior to data transmission. Further, these controlsignals are transmitted in SCCHs (Shared Control Channel). SCCHs areprovided in the number of mobile stations to which data is transmittedin the subframe, and the number of mobile stations per subframe isdefined by, for example, frequency bandwidths available in thecommunication system. That is, at the beginning of each subframe, SCCHsin the same number as data channels in the subframe, is multiplexed overthe same time.

Then, studies are underway to adopt frequency scheduling transmissionand frequency diversity transmission to the SCCHs recently (seeNon-patent Document 1). That is, studies are conducted to performlocalized mapping and distributed mapping on a control signaltransmitted in the SCCHs. In this case, control signals transmitted inthe SCCHs include mapping methods of the control signals. Then, mobilestations receiving these control signals identify the content of thesecontrol signals by comparing these received control signals against allpatterns that combinations of the mapping methods and the informationcontents can adopt one to one. That is, the mobile station performsblind detection of the control signal in the SCCHs.

-   Non-patent Document 1: 3GPP RAN WG1 Meeting document, R1-063177

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

For example, a case is assumed where, as shown in FIG. 1, four SCCHs arefrequency-domain-multiplexed to subcarriers f₁ to f₁₆ forming one OFDMsymbol such that three SCCHs (SCCH 1 to SCCH 3) are subject to localizedmapping and one SCCH is subject to distributed mapping. That is, a caseis assumed here where localized mapping and distributed mapping aremixed in communication resources of the frequency domain. This mappingpattern is reported to the mobile stations in advance.

Further, a case is assumed here where, in each mobile stations, thereare three types of control information, that is, (1) DL (downlink) andnon-MIMO (Multiple-Input Multiple-Output) allocation information (2) DLand MIMO allocation information (3) UL (uplink) allocation informationand four kinds on MCSs.

The mobile station performs blind detection for control signalsaccording to the mapping pattern to be reported (FIG. 1), so that themobile station needs to try blind detection forty eight times in total,that is, three times (SCCH 1 to 3)×three times (types of controlinformation)×four times (MCSs)=thirty six times for localized mapping,and one time (SCCH 4)×three times (types of control information)×fourtimes (MCSs)=twelve times for distributed mapping.

In this way, the mobile stations need to try blind detection a largenumber of times, that is, forty eight times, and therefore, have toconsume a large amount of power by blind detection for control signals.

It is therefore an object of the present invention to provide abasestation and control signal mapping method that can reduce the number ofdetections on the control signals in the mobile stations and suppresspower consumption of the mobile stations.

Means for Solving the Problem

The base station of the present invention adopts a configurationincluding: a setting section that sets up a mapping method associatedwith a MCS of a control signal or information content of the controlsignal; and a mapping section that maps the control signal tocommunication resources according to the mapping method set up.

Advantageous Effect of the Invention

According to the present invention, it is possible to reduce the numberof detections on the control signals in the mobile stations and suppresspower consumption of the mobile stations.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an example of a mapping pattern (example 1);

FIG. 2 is a block diagram showing the configuration of the base stationaccording to Embodiment 1;

FIG. 3 is a mapping table according to Embodiment 1;

FIG. 4 is a block diagram showing the configuration of the base stationaccording to Embodiment 2;

FIG. 5 is a mapping table according to Embodiment (example 1);

FIG. 6 is a mapping table according to Embodiment (example 2);

FIG. 7 is an example of a mapping pattern (example

FIG. 8 is an example of a mapping pattern (example 3); and

FIG. 9 illustrates a communication resource example.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, embodiments of the present invention will be described in detailwith reference to the accompanying drawings.

Embodiment 1

FIG. 2 shows the configuration of base station 100 of the presentembodiment. Base station 100 multiplexes a plurality of SCCHs over thesame time.

In base station 100, encoding and modulating sections 101-1 to 101-n,each formed with encoding section 11 and modulating section 12 used foran SCCH, encoding and modulating sections 103-1 to 103-n, each formedwith encoding section 21 and modulating section 22 used for a datachannel, and demodulating and decoding sections 113-1 to 113-n, eachformed with demodulating section 31 and decoding section 32, areprovided in the number of mobile stations n with which base station 100can communicate. Further, encoding and modulating sections 101-1 to101-n, encoding and modulating sections 103-1 to 103-n, and demodulatingand decoding sections 113-1 to 113-n, are provided for mobile stations 1to n, respectively.

MCS setting section 121 sets up the MCSs in encoding and modulatingsections 101-1 to 101-n. MCS setting in MCS setting section 121 will bedescribed later in detail.

In encoding and modulating sections 101-1 to 101-n, according to MCSsset up by MCS setting section 121, encoding sections 11 encode (i.e.perform a CRC (Cyclic Redundancy Check) encoding and error correctingencoding) control signals per mobile station transmitted in the SCCHsper mobile station, and modulating sections 12 modulate the controlsignals after encoding according to MCSs set up by MCS setting section121 and output the modulated control signals to mapping section 102.

Mapping setting section 122 sets up a mapping method in mapping section102, that is, the mapping method of control signals. Further, mappingsetting sect ion 122 outputs received quality information received asinput from decoding sections 32 (described later) to mapping section102. Mapping method setting in mapping setting section 122 will bedescribed later in detail.

According to mapping method set up by mapping setting section 122,mapping section 102 maps the control signals for the mobile stations toa plurality of subcarriers forming an OFDM symbol and outputs the mappedcontrol signals to multiplexing section 105. That is, mapping section102 maps the SCCH for each mobile station to one of a plurality ofsubcarriers forming an OFDM symbol. This mapping processing in mappingsection 102 allows a plurality of SCCHs to befrequency-domain-multiplexed over the same time. The mapping process inmapping section 102 will be explained in detail.

In encoding and modulating sections 103-1 to 103-n, encoding sections 21encode (i.e. perform a CRC encoding and error correcting encoding)transmission data per mobile station and modulating sections 22 modulatethe transmission data after encoding and output the modulatedtransmission data to allocating section 105. The MCSs at this timefollow MCS information received as input from adaptive control section114.

According to the control from adaptive control section 114, mappingsection 104 maps data for mobile stations to one of a plurality ofsubcarriers forming an OFDM symbol and outputs the mapped data tomultiplexing section 105. At this time, mapping section 104 maps datafor mobile stations to one of a plurality of subcarriers in resourceblock units. Further, mapping section 104 outputs the mobile station IDsand resource block numbers as mapping result information for data(information showing which data for which mobile station is mapped towhich resource blocks) to control signal generating section 115.

MCS setting section 121 and encoding section 123 receive as inputinformation of a mapping table, in which the associations between aplurality of MCSs having different MCS levels and a plurality of mappingmethods are setup (i.e. mapping table information). This mapping tableinformation is reported from a radio communication control stationapparatus (i.e. Radio Network Controller) that is located in a higherlayer than base station 100. Further, this mapping table information istransmitted from base station 100 to the mobile stations with a BCH(i.e. Broadcast Channel), a DPCCH (Dedicated Physical Control Channel),a RRC signaling (Radio Resource Control) and so on.

Encoding section 123 encodes the mapping table information andmodulating section 124 modulates the mapping table information afterencoding and outputs the modulated mapping table informationmultiplexing section 105.

Multiplexing section 105 time-domain-multiplexes the data received asinput from mapping section 104, the control signals received as inputfrom mapping section 102, the mapping table information received asinput from modulating section 124 and pilots and outputstime-domain-multiplexed data to IFFT (Inverse Fast Fourier Trans form)section 106. The control signals are multiplexed, for example, everysubframe, and multiplexed at the beginning of every subframe. Themapping table information is multiplexed, for example, upon the initialsignaling after the mobile stations start communication. The pilots aremultiplexed at predetermined time intervals.

IFFT section 106 performs an IFFT on the control signals mapped to aplurality of subcarriers or the data mapped to a plurality ofsubcarriers, to generate an OFDM symbol, which is a multicarrier signal.That is, IFFT section 106 generates an OFDM symbol where a plurality ofSCCHs are frequency-domain-multiplexed or an OFDM symbol where aplurality of data channels are frequency-domain-multiplexed. Further,the OFDM symbol formed with the SCCHs and the OFDM symbol formed withthe data channels are time-domain-multiplexed in one subframe. Further,IFFT section 106 performs an IFFT on the mapping table information andthe pilots, to generate an OFDM symbol. The mapping table information ismapped to a specific subcarrier in one OFDM symbol and the pilots aremapped to all subcarriers in one OFDM symbol.

CP (Cyclic Prefix) addition section 107 attaches the same signal as thetail part of the OFDM symbol, to the beginning of that OFDM symbol, as aCP.

Radio transmitting section 108 performs transmission processingincluding D/A conversion, amplification and up-conversion, on the OFDMsymbol with an attachment of a CP and transmits the OFDM symbol with aCP from antenna 109 to the mobile stations.

On the other hand, radio receiving section 110 receives via antenna 109maximum n OFDM symbols transmitted at the same time from a maximum of nmobile stations, and performs receiving processing includingdown-conversion and A/D conversion on these OFDM symbols.

CP removing section 111 removes the CPs from the OFDM symbols afterreceiving processing.

FFT (Fast Fourier Transform) section 112 performs an FFT on the OFDMsymbols after the CP removal to obtain the mobile station-specificsignals multiplexed in the frequency domain. Here, the mobile stationstransmit signals using different subcarriers or different resourceblocks, and the mobile station-specific signals include received qualityinformation reported from the mobile stations. Each mobile station isable to measure received quality from, for example, the received SNR,received SIR, received SINR, received CINR, received power, interferencepower, bit error rate, throughput, MCS that achieves a predeterminederror rate, and so on. In addition, received quality information may bereferred to as “CQI (Channel Quality Indicator)” or “CSI (Channel StateInformation),” for example.

In demodulating and decoding sections 113-1 to 113-n, demodulatingsections 31 modulate the signal after an FFT and, decoding sections 32decode the signal after demodulation, to acquire received data. Receivedquality information in the received data is received as input toadaptive control section 114, MCS setting section 121 and mappingsetting section 122.

Based on the received quality information reported from the mobilestations, adaptive control section 114 performs adaptive control on thetransmission data for the mobile stations. That is, based on thereceived quality information, adaptive control section 114 selects theMCS that can achieve the required error rate for encoding and modulatingsections 103-1 to 103-n and outputs the MCS information. This adaptivecontrol is carried out every resource block. That is, adaptive controlsection 114 performs adaptive control on data channels every severalresource blocks. Further, based on the received quality information,adaptive control section 114 determines for mapping section 104, towhich the resource blocks transmission data for the mobile stations ismapped, using scheduling algorithms such as the maximum SIR method andthe proportional fairness method. Further, adaptive control section 114outputs the MCS information per mobile station to control signalgenerating section 115.

Control signal generating section 115 generates control signals permobile station formed with the mapping result information per mobilestation, the MCS information per mobile station and the types of controlinformation of the control signals, and outputs the generated controlsignals to corresponding encoding sections 11. As described above, thereare three types of control information, that is, (1) DL and non-MIMOallocation information, (2) DL and MIMO allocation information and, (3)UL allocation information, and control signal generating section 115selects one of the three types of control information.

Next, the MCS setting in MCS setting section 121, the mapping methodsetting in mapping setting section 122 and the mapping in mappingsection 102 will be described in detail.

With regards to the modulation scheme, the modulation level becomeshigher (i.e. M-ary modulation number is larger) when the MCS level ishigher, and, with regards to the coding rate, the coding rate becomeshigher when the MCS level is higher. That is, the transmission rate(i.e. bit rate) increases when the MCS level is higher. Meanwhile, errorrate performances degrade.

Here, received quality in mobile stations located near a cell boundaryis susceptible to the influence of the fluctuation of interference fromneighboring cells, and therefore, the accuracy of received qualityinformation per frequency band becomes poor in mobile stations locatednear a cell boundary. Consequently, distributed mapping, which does notrequire received quality information, is a suitable mapping method formobile stations located near a cell boundary. On the other hand,received quality in mobile stations located near the center of a cell isnot susceptible to the influence of the fluctuation of interference fromneighboring cells, and therefore, the accuracy of received qualityinformation per frequency band is good in the mobile stations locatednear the center of a cell. Consequently, localized mapping, which isperformed based on received quality information per frequency band, is asuitable mapping method for mobile stations located near the center of acell.

Further, it is necessary for the SCCHs for mobile stations located neara cell boundary to set up a MCS having a low MCS level to fulfill therequired received quality. On the other hand, even if a MCS having ahigh MCS level is set up for the SCCHs for mobile stations located nearthe center of a cell, it is possible to fulfill the required receivedquality.

It naturally follows from the above that distributed mapping is suitablefor the SCCHs for mobile stations located near a cell boundary, that is,the SCCHs in which a MCS having a low MCS level is set up, and localizedmapping is suitable for the SCCHs for mobile stations located near thecenter of a cell, that is, SCCHs in which a MCS having a high MCS levelis set up.

Now, with the present embodiment, the SCCHs are mapped and MCSs are setup for the SCCHs as below.

In the following explanation, as described above, the mapping patternshown in FIG. 1 is reported to mobile stations in advance. Further, asdescribed above, four SCCHs are frequency-domain-multiplexed in one OFDMsymbol. That is, the number of mobile stations allocated per subframe isfour.

FIG. 3 shows the mapping table according to the present embodiment. Inthis mapping table, MCS 1 is the lowest MCS level and MCS 4 is thehighest MCS level among MCS 1 to MCS 4. That is, in this mapping table,associations between the MCSs having low MCS levels and distributedmapping are provided and associations between the MCSs having high MCSlevels and localized mapping are provided. These associations areprovided in advance such that the number of times blind detection isperformed for the control signals by the mobile stations is equal orless than a predetermined value. For example, in the present embodiment,the associations are provided in advance such that the number of timesblind detection is performed in the mobile stations is less than half ofa case where the associations are not provided.

For example, mapping setting section 122 finds average received qualityper mobile station in the entire frequency band (that is, subcarriers f₁to f₁₆), and, sets up localized mapping for the control signal mappingmethod for the mobile stations having the top three average receivedquality (hereinafter “upper mobile stations”) and sets up distributedmapping for the control signal mapping method for the mobile stationhaving the bottom averaged received quality (hereinafter “the lowestmobile station”). Then, mapping setting section 122 outputs the settingresult to mapping section 102 and MCS setting section 121.

According to the setting result in mapping setting section 122, mappingsection 102 maps control signals for the upper three mobile stations toone of SCCH 1 to SCCH 3 shown in FIG. 1, and maps the control signal forthe lowest mobile station to SCCH 4.

At this time, mapping section 102 compares average received quality ofthe frequency band corresponding to SCCH 1 (i.e. subcarriers f₂ to f₅)between the upper three mobile stations, and maps the control signal forthe mobile station of the highest received quality to SCCH 1. Further,mapping section 102 compares average received quality of the frequencyband corresponding to SCCH 2 (i.e. subcarriers f₇ to f₁₀) between theremaining upper two mobile stations, and maps the control signal for themobile station of higher average received quality to SCCH 2. Then,mapping section 102 maps the control signal for the remaining upper onemobile station to SCCH 3.

Meanwhile, according to the setting result in mapping setting section122, MCS setting section 121 selects one MCS out of four MCSs for thecontrol signals for the four mobile stations, with reference to themapping table of FIG. 3 represented as the mapping table information.That is, MCS setting section 121 sets up MCSs having lower MCS levels,that is, MCS 1 or MCS 2, for the control signals for which distributedmapping is set up, and sets up the MCS having higher MCS levels, thatis, MCS 3 or MCS 4, for the control signals for which localized mappingis set up.

Further, as for the control signals for which distributed mapping is setup, MCS setting section 121 finds average received quality of the entirefrequency band of the mobile stations to which control signals aretransmitted (i.e. subcarriers f₁ to f₁₆), and sets up MCS 1 when thisaverage received quality is less than the threshold value TH 1 and setsup MCS 2 when this average received quality is equal or greater than thethreshold value TH 1. Further, as for the control signals for whichlocalized mapping is setup, MCS setting section 121 finds averagereceived quality of the frequency bands corresponding to the SCCHs towhich the control signal is mapped, and sets up MCS 3 when this averagereceived quality is less than the threshold value TH 2 and sets up MCS 4when this average received quality is equal or greater than thethreshold value TH 2. The relationship between the threshold values isTH 1<TH 2.

In this way, according to the present embodiment, control signals aremapped to communication resources of the frequency domain according tothe mapping methods associated with the MCSs of the control signals.

By mapping control signals as such, the number of times of blinddetections in the mobile stations receiving control signals is asfollows. Here, as described above, there are three types of controlinformation per mobile station.

In the present embodiment, distributed mapping is associated with twoMCSs, that is, MCS 1 and MCS 2, and localized mapping is associated withtwo MCSs, that is, MCS 3 and MCS 4. Consequently, the mobile stationscan decide the mapping method and decide the MCS together. That is, ifthe mapping method is decided to be distributed mapping, the mobilestations need only to try blind detection two times for a MCS decision,for MCS1 and for MCS 2, and, similarly, if the mapping method is decidedto be localized mapping, the mobile stations need only to try blinddetection two times for a MCS decision, for MCS 3 and MCS 4.

Consequently, in the mobile stations performing blind detection for thecontrol signals according to the mapping pattern to be reported (FIG.1), it is only necessary to try twenty four times of blind detection intotal, that is, three times (SCCH 1 to 3)×three times (types of controlinformation)×two times (MCSs)=eighteen times for localized mapping, andone time (SCCH 4)×three times (types of control information)×two times(MCSs)=six times for distributed mapping. That is, the number of timesblind detection is performed for the control signals in the mobilestations is reduced by half compared to forty eight times in aconventional case.

In this way, according to the present embodiment, the mapping methods ofcontrol signals and the MCSs of control signals are associated, so thatit is possible to reduce the number of detections on control signals inthe mobile stations. Consequently, according to the present embodiment,it is possible to reduce power consumption of the mobile stations.

Further, according to the present embodiment, MCSs suitable for mappingmethods are set up such that distributed mapping is set up for controlsignals for which MCSs having low MCS levels are set up and localizedmapping is set up for control signals for which MCSs having high MCSlevels are set up, so that it is possible to improve the transmissionefficiency of SCCHs.

Although a case has been explained above where two MCSs are associatedwith distributed mapping and localized mapping apiece, one MCS may beassociated with distributed mapping and localized mapping apiece. Inthis case, the number of times blind detection is performed in eachmobile station is twelve times in total, that is, three times (SCCH 1 to3)×three times (types of control information)×one time (MCS)=nine timesfor localized mapping, and one time (SCCH 4)×three times (types ofcontrol information)×one time (MCS)=three times for distributed mapping.Therefore, it is possible to reduce the number of times of detectionsfurther on the control signals in the mobile stations. In this case, inthe setting of MCSs of control signals, comparison between averagereceived quality in MCS setting section 121 and threshold values is notnecessary.

Embodiment 2

With this embodiment, the control signals are mapped to communicationresources of the frequency domain according to the mapping methodsassociated with information contents of the control signals.

FIG. 4 shows the configuration of base station 300 of the presentembodiment. In FIG. 4, the same components will be assigned the samereference numerals as in FIG. 2 (Embodiment 1), therefore thedescription thereof will be omitted.

Decoding sections 32 output received quality information in receiveddata to adaptive control section 114.

Control signal generating section 115 outputs the selected type ofcontrol information to mapping setting section 301 in addition toprocessing explained in Embodiment 1.

Mapping setting section 301 and encoding section 123 receive as inputinformation of a mapping table in which the associations between aplurality of different types of control information and a plurality ofmapping methods are setup (i.e. mapping table information). This mappingtable information is reported from a radio communication control stationapparatus that is located in a higher layer than base station 300.Further, this mapping table information is transmitted from base station300 to the mobile stations with a BCH, a DPCCH, a RRC signaling and soon.

Mapping setting section 301 sets up mapping methods in mapping section302, that is, mapping methods of control signals.

According to mapping method set up by mapping setting section 301,mapping section 302 maps the control signals for the mobile stations toa plurality of subcarriers forming an OFDM symbol, and outputs themapped control signals to multiplexing section 105. That is, mappingsection 302 maps the SCCH for each mobile station to one of a pluralityof subcarriers forming an OFDM symbol. This mapping processing inmapping section 302 allows a plurality of SCCHs to befrequency-domain-multiplexed over the same time.

Next, the mapping method setting in mapping setting section 301 and themapping in mapping section 302 will be described in detail.

As described above, distributed mapping, which does not require receivedquality information, is a suitable mapping method for mobile stationslocated near a cell boundary. On the other hand, localized mapping,which is performed based on received quality per frequency band, is asuitable a mapping method for mobile stations located near the center ofa cell.

Further, non-MIMO transmission is more likely to be applied to mobilestations, which are located near a cell boundary and which are difficultto be divided in space due to the influence of interference fromneighboring cells. On the other hand, MIMO transmission is more likelyto be applied to mobile stations, which are located near the center of acell and which have little interference from neighboring cells and canbe divided in space accurately.

It naturally follows from the above that distributed mapping is suitablefor the SCCHs for mobile stations located near a cell boundary, that is,the SCCHs for mobile stations to which non-MIMO transmission is applied,and, localized mapping is suitable for the SCCHs for mobile stationslocated near the center of a cell, that is, the SCCHs for mobilestations to which MIMO transmission is applied.

Further, although uplink data is present at the timing uplink isallocated is possible that downlink data is not present. That is, at thetiming uplink is allocated, it is possible not to report receivedquality information for performing frequency scheduling transmission ondownlink data from mobile stations to the base station. Consequently,distributed mapping that does not require received quality informationis suitable for the SCCHs formed with uplink allocation information.

Then, with the present embodiment, the SCCHs are mapped as follows.

In the following explanation, as described above, the mapping patternshown in FIG. 1 is reported to mobile stations in advance. Further, asdescribed above, four SCCHs are frequency-domain-multiplexed in one OFDMsymbol. That is, the number of mobile stations allocated per subframe isfour.

Further, a case is assumed where there are four kinds of MCSs.

FIG. 5 shows the mapping table according to the present embodiment. Thatis, in this mapping table, associations between UL allocationinformation and distributed mapping are provided, associations betweenDL and non-MIMO allocation information and distributed mapping areprovided, and associations between DL and MIMO allocation informationand localized mapping are provided. That is, in this mapping table,associations between the types of control information, that is, theinformation contents of control signals, and control signal mappingmethods are provided. Similar to Embodiment 1, these associations areprovided in advance such that the number of times blind detection isperformed for the control signals by the mobile stations is equal orless than a predetermined value. For example, in the present embodiment,similar to Embodiment 1, the associations are provided in advance suchthat the number of times blind detection is performed in the mobilestations is less than half of a case where the associations are notprovided.

According to the type of control information received as input fromcontrol signal generating section 115, with reference to the mappingtable of FIG. 5 represented as the mapping table information, and,mapping setting section 301 sets up the mapping method for controlsignals where the type of control information is UL allocationinformation to be distributed mapping, sets up the mapping method forcontrol signals where the type of control information is DL and non-MIMOallocation information to be distributed mapping, and sets up themapping method for control signals where the type of control informationis DL and MIMO allocation information to be localized mapping. That is,mapping setting section 301 sets up localized mapping for controlsignals including allocation information for MIMO transmission (i.e. DLand MIMO allocation information), and sets up distributed mapping forcontrol signals not including allocation information for MIMOtransmission (i.e. DL and MIMO allocation information). Further, mappingsetting section 301 sets up distributed mapping for control signalsincluding allocation information for uplink (i.e. uplink allocationinformation). Then, mapping setting section 301 outputs the settingresult to mapping section 302.

According to the setting result in mapping setting section 301, mappingsection 302 maps the control signals for the mobile stations to one ofSCCH 1 to 4 shown in FIG. 1.

In this way, according to the present embodiment, control signals aremapped to communication resources of the frequency domain according tothe mapping methods associated with the types of control information ofcontrol signals.

By mapping control signals as such, the number of times of blinddetections in the mobile stations receiving control signals is asfollows.

In the present embodiment, distributed mapping is associated with ULallocation information and DL and non-MIMO allocation information, andlocalized mapping is associated with DL and MIMO allocation information.Consequently, the mobile stations can decide the mapping method anddecide the type of control information together. That is, if the mappingmethod is decided to be distributed mapping, the mobile stations needonly to try blind detection two times for a decision of a type ofcontrol information, for UL allocation information and DL and non MIMOallocation information, and, similarly, if the mapping method is decidedto be localized mapping, the mobile stations need only to try blinddetection one time for a decision of a type of control information, forDL and MIMO-allocation information.

Consequently, in the mobile stations performing blind detection for thecontrol signals according to the mapping pattern to be reported (FIG.1), it is only necessary to try twenty times of blind detection intotal, that is, three times (SCCH 1 to 3)×one time (type of controlinformation)×four times (MCSs)=twelve times for localized mapping, andone time (SCCH 4)×two times (types of control information)×four times(MCSs)=eight times for distributed mapping. That is, the number of timesblind detection is performed for the control signals in the mobilestations is reduced by half compared to forty eight times in aconventional case.

In this way, according to the present embodiment, the mapping methods ofcontrol signals and the types of control information of control signalsare associated, so that it is possible to reduce the number ofdetections on control signals in the mobile stations. Consequently,according to the present embodiment, similar to Embodiment 1, it ispossible to reduce power consumption of the mobile stations.

In the case where, whether MIMO transmission or non-MIMO transmission isperformed is known in the mobile stations in advance, the number oftimes blind detection is performed in the mobile stations is as follows.In this case, the number of times blind detection is performed in themobile station to be subject to MIMO transmission is sixteen times intotal, that is, three times (SCCH 1 to 3)×one time (type of controlinformation)×four times (MCSs)=twelve times for localized mapping, andone time (SCCH 4)×one time (types of control information)×four times(MCS)=four times for distributed mapping. Therefore, it is possible toreduce the number of times of detections further on the control signalsin the mobile stations.

Further, in the case where there are only two types of controlinformation, that is, (1) DL and non-MIMO allocation information and (2)DL and MIMO allocation information, the mapping methods may be set up inthe same way as above using the mapping table shown in FIG. 6. In thiscase, in the mobile stations performing blind detection for the controlsignals according to the mapping pattern to be reported (FIG. 1), it isonly necessary to try sixteen times of blind detection in total, thatis, three times (SCCH 1 to 3)×one time (type of controlinformation)×four times (MCSs)=twelve times for localized mapping, andone time (SCCH 4)×one time (types of control information)×four times(MCSs)=four times for distributed mapping. Further, in the case where,whether MIMO transmission is conducted or non-MIMO transmission isconducted is known in the mobile stations in advance, the number oftimes blind detection is performed in the mobile stations subject toMIMO transmission is sixteen times in total, that is, three times (SCCH1 to 3)×one time (type of control information)×four times (MCSs)=twelvetimes for localized mapping, and one time (SCCH 4)×one time (type ofcontrol information)×four times (MCSs)=four times for distributedmapping. The number of times blind detection is performed in the mobilestations subject to non-MIMO transmission is, one time (SCCH 4)×one time(type of control information)×four times (MCSs)=four times. Therefore,it is possible to reduce the number of times of detections further onthe control signals in the mobile stations.

Further, the DL and MIMO allocation information may be furtherclassified into SU-MIMO (Single-User-MIMO) information allocationinformation and MU-MIMO (Multi-User-MIMO) information allocationinformation.

Embodiments of the present invention have been explained.

The present invention may be implemented to combine Embodiment 1 andEmbodiment 2. By implementing the combination, it is possible to reducethe number of detections further on control signals in the mobilestations.

Further, although a mapping pattern (FIG. 1) in which localized mappingand distributed mapping are mixed in communication resources of thefrequency domain is shown in the above description, a mapping pattern(FIG. 7), in which four SCCHs (SCCH 1 to SCCH 4) are subject tolocalized mapping to subcarriers f₁ to f₁₅ forming one OFDM symbol andonly localized mapping is present in communication resources of thefrequency domain, and, a mapping pattern (FIG. 8), in which four SCCHs(SCCH 1 to SCCH 4) are subject to distributed mapping to subcarriers f₁to f₁₆ forming one OFDM symbol and only distributed mapping is presentin communication resources of the frequency domain, are implemented bythe present invention. Whether one of a mapping pattern of FIG. 1,mapping pattern in FIG. 7 and a mapping pattern in FIG. 8 is employed isreported from the base station to the mobile stations in advance with aBCH, a DPCCH, a RRC signaling and so on. When the mapping pattern shownin FIG. 7 or the mapping pattern FIG. 8 is employed, the mobile stationsneed only to perform blind detection for only one of localized mappingand distributed mapping, so that it is possible to reduce the number ofdetections further on the control signals in the mobile stations.

Further, the communication resources may be defined not only byfrequency, and may be defined by time and frequency as shown in FIG. 9.

Further, the mapping methods to be allocated may be determined permobile station in advance. For example, the mapping methods aredetermined in advance such that localized mapping is set up for mobilestations near the center of a cell and distributed mapping is set up formobile stations near a cell boundary. By this means, the mobile stationsneed only to perform blind detection for only one of localized mappingand distributed mapping, so that it is possible to reduce the number ofdetections further on the control signals in the mobile stations.

Further, each mobile station may limit the SCCHs to be subject to blinddetection in advance. For example, in FIG. 1, it is determined inadvance that a mobile station receives SCCH 1 only and another mobilestation receives SCCH 2 only. By this means, the mobile stations needonly to perform blind detection for specific SCCHs alone, so that it ispossible to reduce the number of detections further on the controlsignals in the mobile stations.

Further, the subframe used in the above description may be anothertransmission time unit, for example, a time slot or a frame.

Further, the resource block used in the above description may be anothertransmission unit in the frequency domain, for example, a subcarrierblock.

Further, a mobile station may be referred to as “UE,” base station maybe referred to as “Node-B,” and a subcarrier may be referred to as“tone.” Further, a resource block may be referred to as a “subband”, a“subcarrier block”, a “subchannel,” or a “chunk.” Further, a CP may bereferred to as a “guard interval (GI).”

Further, in the SCCH, control signals such as uplink channel allocationinformation, an Ack/Nack signal, PI (Paging Indicator) and a randomaccess response, besides a mobile station ID, an resource block numberand MCS information may be transmitted.

Further, the present invention may be applied to all channels in whichradio communication apparatuses of the receiving side have to detecttransmission information and transmission parameters by blind detection.

Further, although control information for one mobile station istransmitted in one SCCH in the above explanation, a plurality of mobilestations may be grouped and one SCCH is used per group.

Further, although an example has been explained with the aboveexplanation, where the SCCH is allocated at the beginning of a subframe,the SCCH may be allocated to positions that are not the beginning of thesubframe, that is, the second OFDM symbol in a subframe for example.

Further, the SCCH multiplexing method is not limited to frequencymultiplexing, and, may be for example, code multiplexing.

Further, the transform method between the frequency domain and the timedomain is not limited to an IFFT or FFT.

Further, although cases have been described with the above embodiment asexamples where the present invention is configured by hardware, thepresent invention can also be realized by software.

Each function block employed in the description of each of theaforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSIs, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of a programmableFPGA (Field Programmable Gate Array) or a reconfigurable processor whereconnections and settings of circuit cells within an LSI can bereconfigured is also possible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2007-001726, filed onJan. 9, 2007, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention is applicable to, for example, mobile stationcommunication systems.

1. A terminal apparatus, comprising: a receiver structured to receive acontrol channel, which is mapped to a first resource defined byfrequency and time in accordance with a mapping method, and to receivedownlink data mapped to a second resource in accordance with downlinkassignment information, wherein the control channel includes a firstcontrol channel carrying the downlink assignment information indicatingthe second resource to which downlink data is allocated and a secondcontrol channel carrying uplink assignment information indicating athird resource to which uplink data is allocated; and a detectorstructured to detect the control channel, wherein: the mapping method isone of a localized mapping and a distributed mapping; the first controlchannel carrying the downlink assignment information is mapped to afirst region of the first resource; the second control channel carryingthe uplink assignment information is mapped to a second region of thefirst resource, the first region being different from the second region;and the control channel is mapped to an OFDM symbol other than at abeginning of a subframe.
 2. The terminal apparatus according to claim 1,wherein one of the distributed mapping and the localized mapping is setas the mapping method according to a modulation and coding scheme levelfor the control channel.
 3. The terminal apparatus according to claim 1,wherein one of the localized mapping and the distributed mapping is setas the mapping method according to whether the control channel includesassignment information for multiple-input multiple-output transmission.4. The terminal apparatus according to claim 1, wherein the distributedmapping is set as the mapping method for the second control channelcarrying the uplink assignment information.
 5. The terminal apparatusaccording to claim 1, wherein each of different modulation and codingschemes for the control channel is associated with one of thedistributed mapping and the localized mapping.
 6. The terminal apparatusaccording to claim 1, wherein each of the first control channel carryingthe downlink assignment information and the second control channelcarrying the uplink assignment information is associated with one of thedistributed mapping and the localized mapping.
 7. The terminal apparatusaccording to claim 1, wherein each of different modulation and codingschemes for the control channel is associated with one of thedistributed mapping and the localized mapping such that a number oftimes of detection on the control channel is equal to or less than apredetermined value.
 8. The terminal apparatus according to claim 1,wherein each of the first control channel including the downlinkassignment information and the second control channel including theuplink assignment information is associated with one of the distributedmapping and the localized mapping such that a number of times ofdetection on the control channel is equal to or less than apredetermined value.
 9. The terminal apparatus according to claim 1,wherein the downlink assignment information or the uplink assignmentinformation indicates a resource block to which data to the terminalapparatus is allocated, and the control channel includes anidentification of the terminal apparatus and information on a modulationand coding scheme.
 10. The terminal apparatus according to claim 1,wherein in the distributed mapping, the control channel is mapped in adistributed fashion to a frequency domain, and in the localized mapping,the control channel is mapped in a localized fashion to the frequencydomain.
 11. The terminal apparatus according to claim 1, where in thecontrol channel is mapped to the first resource per time slot.
 12. Amethod for detecting a control channel comprising: receiving the controlchannel, which is mapped to a first resource defined by frequency andtime in accordance with a mapping method; detecting, by a processor, thecontrol channel; and receiving downlink data mapped to a second resourcein accordance with downlink assignment information, wherein the controlchannel includes a first control channel carrying the downlinkassignment information indicating the second resource to which downlinkdata is allocated and a second control channel carrying uplinkassignment information indicating a third resource to which uplink datais allocated, wherein: the mapping method is one of a localized mappingand a distributed mapping; the first control channel carrying thedownlink assignment information is mapped to a first region of the firstresource; the second control channel carrying the uplink assignmentinformation is mapped to a second region of the first resource, thefirst region being different from the second region; and the controlchannel is mapped to an OFDM symbol other than at a beginning of asubframe.